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Ann Thorac Surg 1999;67:1001-1005
© 1999 The Society of Thoracic Surgeons

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Original Articles

Minimally invasive versus conventional aortic valve operations: a prospective study in 120 patients

^a Departments of Department of Cardiac Surgery, Karl-Franzens University Graz, Graz, Austria
^b Department of Cardiac Anesthesia, Karl-Franzens University Graz, Graz, Austria

Accepted for publication September 13, 1998.

Address reprint requests to Dr Mächler, Department of Cardiac Surgery, Karl-Franzens University Graz, Auenbruggerplatz 29, A-8036 Graz, Austria
e-mail: heinrich.maechler{at}kfunigraz.ac.at

	Abstract

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Background. Risk evaluation comparing the minimally invasive and standard aortic valve operations has not been studied.

Methods. Four surgeons were randomly assigned to perform the minimally invasive (L-shaped sternotomy) (group 1) or the conventional (group 2) operation in 120 patients exclusively.

Results. In both groups (n = 60) a CarboMedics prothesis was implanted in 90% of patients. There was no significant difference in the cross-clamping period (group 1, 60 minutes; range, 35 to 116 minutes), in the duration of extracorporal circulation (group 1, 84 minutes; range, 51 to 179 minutes) or in the time from skin-to-skin (group 1, 195 minutes; range, 145 to 466 minutes). Patients in group 1 were extubated earlier (p < 0.001), the postoperative blood loss was less (p < 0.001), and the need for analgesics was reduced (p < 0.05). In 5 patients in group 1 a redo operation was required for bleeding (p > 0.05), 3 patients in group 1 required a redo operation because of paravalvular leakage or endocarditis (p > 0.05), the 30-day mortality rate was 1.6%. Overall the survival rate was 95% in group 1 and 97% in group 2 (mean follow-up, 294 days; range, 30 to 745 days).

Conclusion. The advantages of minimally invasive aortic valve operation include reduced trauma from incision and duration of ventilation, decreased blood loss and postoperative pain, the avoidance of groin cannulation, and a cosmetically attractive result. Simple equipment is used with a high degree of effectiveness and with no sacrifice of safety. Our study demonstrated the practicability and reliability of this new method.

	Introduction

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
During the past 2 years, there has been increasing interest in the development of minimally invasive cardiac procedures, for a number of well-known reasons. Since January 1996, when Cosgrove and Sabik [1] and Konertz and associates [2] used a minimally invasive approach for aortic valve operations to minimize surgical trauma, this technique has failed to become well established and is not routinely practiced. The risks of minimal access aortic valve procedures also have not been studied. To measure the value of the new surgical procedure, we designed a prospective study of patients who have conventional versus minimally invasive aortic valve operations. Our goals were to determine (1) whether the morbidity and mortality of the new procedure exceeds that of a matched control, (2) whether the new approach predisposes patients to unfavorable postsurgical outcome, (3) whether there is a difference in postoperative valve-related complications in both groups, and (4) whether there are differences in postoperative outcomes when both methods are compared.

	Patients and methods

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Between July 1996 and December 1997, a total of 120 adult patients requiring aortic valve procedures were admitted. Two staff surgeons performed the conventional operation and two other staff surgeons used the minimally invasive protocol exclusively.

During this 15-month period the four surgeons were randomly assigned to patients, and the two groups of patients were compared. The patients themselves could not be randomly assigned to a surgeon because both groups of surgeons were convinced of the advantages of their respective methods. As to adverse postoperative outcomes among the surgeons, there was no significant difference in the last 300 procedures before July 1996, as calculated with a quality-control program and shown in an earlier study [3].

The preoperative assessment included a thorough cardiac examination and a search for major perioperative risk factors. All patients had electrocardiography, chest x-ray, echocardiography, coronary angiography, and carotid artery sonography. Patients with acute endocarditis, concomitant procedures (mitral valve procedures, coronary artery bypass grafting, and procedures involving the ascending aorta itself), or need for reoperation were excluded from the study. The CarboMedics prothesis (CarboMedics Inc, Austin, TX), biological valves (Mosaic Bioprosthesis; Medtronic, Minneapolis, MN) or Freestyle bioprothesis (Medtronic) were implanted. With every mechanical prothesis with a diameter of 21 mm or less the CarboMedics R500 prothesis was used. Biological protheses were implanted exclusively in patients older than 70 years. Postoperative arrhythmias were diagnosed by electrocardiographic monitoring in the intensive care unit or in the intermediate care unit after data storage on a patient care system (CMS, Hewlett Packard, Palo Alto, CA). Patients were classified as positive for arrhythmias if arrhythmias persisted postoperatively for more than 30 minutes during a 24-hour period in 1 of the first 5 days. Loss of postoperative drainage bleeding was registered until the 48th postoperative hour. To record postoperative neurologic complications, each patient had one or more neurologic follow-up examinations beginning at the third postoperative hour and ending on the seventh postoperative day. All patients had routine echocardiography 1 week, 1 month, 3 months, and 12 months postoperatively. Discharge was based on preoperatively determined admission to a rehabilitation center and not on the patient’s condition. The follow-up period ended on January 31, 1998.

Operative technique
After oral premedication with 2 mL flunitrazepam, all patients received etomidate 300 mg/kg, fentanyl 10 µg/kg for induction of anesthesia, and 0.3 mg/kg pancuronium bromide for relaxation. Clinical monitoring included seven-lead electrocardiography, arterial pressure, central venous pressure, pulmonary artery catheter, pulse oxymeter, and capnography. Anesthesia was supplemented with isoflurane, up to 0.5% inspired, and bolus doses of fentanyl (50 to 100 µg) as indicated.

A midline skin incision, 8 to 10 cm, was made from the second rib down to the level of the head of the third or fourth rib. The decision to extend the L-shaped sternotomy with the electrical saw with the vertical blade from the notch to the third (pyknic habitus) or fourth intercostal space (leptosome habitus) was based on chest x-ray findings. No attempt was made to identify the right intercostal artery. A pediatric spreader was inserted reversed. The pericardium was opened above the aorta and the right appendage. The ascending aorta was cannulated in a conventional manner. A right-angled venous cannula (40 F, long shaft, DLP, Medtronic) was brought substernally and intrapericardially to the right appendage through a 2-cm subxiphoidal incision (also for postoperative intrapericardial drainage) or by direct episternal cannulation. After institution of the cardiopulmonary bypass using hemodilution and systemic hypothermia of 30°C to 32°C and insertion of the vent (right superior pulmonary vein or pulmonary artery) the aorta was cross-clamped. St. Thomas’ cardioplegia (500 to 700 mL) was applied to the ostia directly after tranverse aortotomy. A subsequent dosage (300 mL) was administered if fibrillation occurred or if the cross-clamping period lasted longer than 75 minutes. Air was removed via the aortotomy and the ascending aorta in normal as well as head-down position. The first 10 patients had transesophageal echocardiography to detect any air bubbles after the air removal. Defibrillation was performed as usual with pediatric defibrillator paddles intrapericardially. In cases of atrioventricular block II or III the usual epicardial VVI-pacing or DDD-pacing wires were applied to the jugular vein along with catheters for measurement of left atrial pressure. The sternum was closed with wires. Patients who received the standard operation had it done through a full sternotomy, high ascending aorta cannulation, right venous cannulation and superior pulmonary vein venting. No retrograde administration of cardioplegia was performed.

Data analysis
Data are presented as median values (minimum to maximum) (lower to upper quartiles). Testing of demographic variables was performed with Fisher’s exact test. Differences of variables between both groups were calculated with the Mann-Whitney U test and Fisher’s exact test.

	Results

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Table 1 shows the demographic data. In the group that had the minimally invasive procedure (group 1), 54 (90%) patients received a CarboMedics prothesis. In 3 patients a Mosaic bioprothesis and in 1 patient a Freestyle bioprothesis was used. In the 2 patients with a subvalvular aortic stenosis a myectomy with commissurotomy was performed.

There was one case of 30-day mortality (stroke) in group 1 and none in group 2. On the seventh postoperative day, the prostheses in all patients were functioning normally. Five patients in group 1 needed a reoperation for bleeding (p > 0.05) (Table 2); two of them had only a subxiphoidal bleeding from the incision, while the others had major bleeding from the aortotomy. In the latter patient we converted to full sternotomy during the revision and he was the only one to have a stroke during this procedure. As mentioned in the methods section, the hospital stay was not shorter in group 1 because the transfer to the rehabilitation center (seventh to tenth day postoperatively) had been arranged preoperatively.

One patient in group 1 needed a reoperation for paravalvular leakage 3 months postoperatively. Two patients in group 1 had early endocarditis within the first 9 weeks postoperatively (Table 1), one patient had late endocarditis 12 months postoperatively. One of these patients died 3 months after the reoperation. Overall the survival rate was 95% in group 1 and 97% in group 2. The follow-up was complete in group 1 and 95% in group 2, with a mean follow-up period of 294 (30 to 745) (122 to 437) days.

	Comment

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
The promise of minimally invasive heart surgery continues to fascinate patients, particularly when it is heard through the mass media [4]. The advantages of these new strategies should be the reduced surgical trauma and pain, shortened hospital stay, and a faster mobilization combined with reduced costs [1, 2, 5, 6]. However, considerable skepticism remains and no study had previously been undertaken to evaluate perioperative risk factors for limited access operations on heart valves.

In our 18 months’ experience with 61 patients in group 1, we found lower morbidity, a 1.6% 30-day mortality rate, and no lengthening of the aortic cross-clamping period, the extracorporal duration, or the time from skin-to-skin (Table 2). The major advantage of our procedure was not merely cosmetic, as in minimally invasive coronary artery bypass procedures, as there were significant improvements regarding the time of ventilation, blood loss, and use of analgesics (Table 2). Moreover, neither the femoral artery nor vein had to be cannulated, and there was no need to sacrifice either of the internal mammary arteries.

However, opinions differ on the best approach for minimally invasive aortic procedures. The disadvantage of parasternal access [1] is the need for femoral cannulation [7, 8], the need to resect the cartilage of the third or fourth rib, and the ligation of the right mammary artery. Recently, Minale and associates [9] reported a procedure that used a parasternal incision that avoided rib resection and groin cannulation. In cases of transverse sternotomy, both mammary arteries must be ligated or dissected down, with potentially high sternal instability. After a longitudinal ministernotomy, Konertz and colleagues [2] introduced the venous cannula through a transsternal port at the caudal portion of the sternotomy. This additional destruction of the sternum that is required to introduce the port is not part of our technique. Our subxiphoidal and substernal introduction of the venous cannula has never been a technical problem.

Regarding the selection of suitable patients, it was shown that the new technique suits all patients, as long as there is no calcifying pericarditis. In a very small patient (body length less than 150 cm) the sternum is short, so just a short part of the caudal sternum remains untouched. The limited access might not be feasible in small patients. The main disadvantage of this technique is the poor air removal, because it is impossible to remove the air over the cardiac apex. In the first 10 patients we did transesophageal sonography intraoperatively. We saw no air pooling, so we considered our air removal technique to have solved the problem of air embolism. However, intraoperative Doppler sonography of the carotids should objectively determine its presence or absence. Generally, we do not recommend routine transesophageal echocardiography, in contrast to Mitchell and associates [10].

Konertz and associates [2] reported transcutaneous defibrillation. We safely performed the intrapericardiac defibrillation with common pediatric defibrillator paddles. The diameter of the paddles was the limitation for the length of skin incision. A main advantage of the described technique is that the caudal sternum remains stable, preserving the integrity of the caudal chest wall, which is advantageous for patients with respiratory insuffiency. Additionally, the pericardium above the ventricles also remains untouched. An ongoing study will determine whether the latter might protect against overstretching during weaning from bypass. However, the untouched pericardium seems to protect against postcardiotomy syndrome; there was only one case of postoperative arrhythmias and pericardial effusions more than 1 cm.

The three cases of endocarditis seem not to be related to the new procedure. No additional instruments or equipment was necessary (Fig 1) [11], nor were special anesthetic routines [12]. The approach described for minimally invasive aortic valve replacement has been introduced as a standard procedure at our institution. In cases of unforeseen problems, conversion to the standard technique is possible immediately without any risk to the patient. Two additional patients had combined procedures on the mitral valve with good visualization provided by an additional incision into the roof of the left atrium and a single venous cannula. However, performing bypass grafting simultaneously with an L-shaped incision seems not to be possible.

View larger version (138K): [in this window] [in a new window]   Fig 1. Simple equipment is used in minimally invasive aortic valve operations in contrast to the instruments used for endoscopic or endoclamp techniques. The instruments displayed are a pediatric spreader, a cannula for the vent, a venous right-angled cannula, and the arterial cannula.

	Footnotes

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
This article has been selected for the open discussion forum on the STS Web site: http://www.sts.org/section/atsdiscussion/

	References

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 

1. Cosgrove D.M., III, Sabik J.F. Minimally invasive approach for aortic valve operations. Ann Thorac Surg 1996;62:596-597.[Abstract/Free Full Text]
2. Konertz W., Waldenberger F., Schmutzler M., Ritter J., Liu J. Minimal access valve surgery through superior partial sternotomy: a preliminary study. J Heart Valve Dis 1996;5:638-640.[Medline]
3. Knez I., Machler M., Rehak P., et al. Concomitant procedures in the small versus standard aortic root. J Heart Valve Dis 1996;3:294-301.
4. SoRelle R. Minimally invasive heart surgery. Circulation 1997;96:2483-2484.
5. Chitwood W.R., Jr, Elbeery J.R., Moran J.F. Minimally invasive mitral valve repair using transthoracic aortic occlusion. Ann Thorac Surg 1997;63:1477-1490.[Abstract/Free Full Text]
6. Schwartz D.S., Ribakove G.H., Grossi E.A., et al. Minimally invasive mitral valve replacement: port-access technique, feasibility and myocardial functional preservation. J Thorac Cardiovasc Surg 1997;113:1022-1030.[Abstract/Free Full Text]
7. Aris A., Padro J.M., Camara M.L. Minimally invasive aortic valve replacement. Rev Española Cardiol 1997;50:778-781.
8. Cosgrove D.M., III, Sabik J.F., Navia J.L. Minimally invasive valve operations. Ann Thorac Surg 1998;65:1535-1539.[Abstract/Free Full Text]
9. Minale C., Reifschneider H.J., Schmitz E., Uckmann F.P. Single access for minimally invasive aortic valve replacement. Ann Thorac Surg 1997;64:120-123.[Abstract/Free Full Text]
10. Mitchell M.B., Brown J.M., London M.J. Cardiac entrapment during minimally invasive aortic valve replacement. Ann Thorac Surg 1997;64:1171-1173.[Abstract/Free Full Text]
11. Tam R.K.W., Almeida A.A. Minimally invasive aortic valve replacement via partial sternotomy. Ann Thorac Surg 1998;65:275-276.[Abstract/Free Full Text]
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Heinrich E. Mächler Bruno Rigler Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mächler, H. E. Articles by Rigler, B. Search for Related Content PubMed PubMed Citation Articles by Mächler, H. E. Articles by Rigler, B.